ipc/sem.c: fully initialize sem_array before making it visible

commit e8577d1f0329d4842e8302e289fb2c22156abef4 upstream.

ipc_addid() makes a new ipc identifier visible to everyone.  New objects
start as locked, so that the caller can complete the initialization
after the call.  Within struct sem_array, at least sma->sem_base and
sma->sem_nsems are accessed without any locks, therefore this approach
doesn't work.

Thus: Move the ipc_addid() to the end of the initialization.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Reported-by: Rik van Riel <riel@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 2.6.32:
 - Adjust context
 - The error path being moved looks a little different]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/ipc/sem.c b/ipc/sem.c
index b781007eea46aa02355303c48c52c071a9931b74..26dc5b1fa64d3ca8edc30802a400034db65906e8 100644 (file)
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -264,6 +264,12 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
                return retval;
        }
 
+       sma->sem_base = (struct sem *) &sma[1];
+       INIT_LIST_HEAD(&sma->sem_pending);
+       INIT_LIST_HEAD(&sma->list_id);
+       sma->sem_nsems = nsems;
+       sma->sem_ctime = get_seconds();
+
        id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
        if (id < 0) {
                security_sem_free(sma);
@@ -272,11 +278,6 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
        }
        ns->used_sems += nsems;
 
-       sma->sem_base = (struct sem *) &sma[1];
-       INIT_LIST_HEAD(&sma->sem_pending);
-       INIT_LIST_HEAD(&sma->list_id);
-       sma->sem_nsems = nsems;
-       sma->sem_ctime = get_seconds();
        sem_unlock(sma);
 
        return sma->sem_perm.id;